file-constants.md

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Learn more about: File Constants	File Constants	11/04/2016	_O_APPEND _O_CREAT _O_EXCL _O_RDONLY _O_RDWR _O_TRUNC _O_WRONLY FCNTL/_O_APPEND FCNTL/_O_CREAT FCNTL/_O_EXCL FCNTL/_O_RDONLY FCNTL/_O_RDWR FCNTL/_O_TRUNC FCNTL/_O_WRONLY	_O_RDWR constant O_EXCL constant O_RDWR constant O_WRONLY constant O_APPEND constant O_CREAT constant _O_CREAT constant _O_APPEND constant _O_EXCL constant O_TRUNC constant _O_RDONLY constant _O_TRUNC constant O_RDONLY constant _O_WRONLY constant	c8fa5548-9ac2-4217-801d-eb45e86f2fa4

File constants

Syntax

#include <fcntl.h>

Remarks

The integer expression formed from one or more of these constants determines the type of reading or writing operations permitted. It's formed by combining one or more constants with a translation-mode constant.

The file constants are as follows:

Constant	Description
_O_APPEND	Repositions the file pointer to the end of the file before every write operation.
_O_CREAT	Creates and opens a new file for writing; the constant has no effect if the file specified by filename exists.
_O_EXCL	Returns an error value if the file specified by filename exists. Only applies when used with _O_CREAT.
_O_RDONLY	Opens file for reading only; if this flag is given, _O_RDWR and _O_WRONLY can't be given.
_O_RDWR	Opens file for both reading and writing; if this flag is given, _O_RDONLY and _O_WRONLY can't be given.
_O_TRUNC	Opens and truncates an existing file to zero length; the file must have write permission. The contents of the file are destroyed. If this flag is given, you can't specify _O_RDONLY.
_O_WRONLY	Opens file for writing only; if this flag is given, _O_RDONLY and _O_RDWR can't be given.

See also

_open, _wopen
_sopen, _wsopen
Global constants